a) Field of the Invention
This invention relates to an outer ring for a one-way clutch which is suitable for use with a hub of a wet-type multiple disk clutch useful in an automatic transmission or which is suitable for use in a conveyor or the like.
b) Description of the Related Art
To facilitate understanding of the present invention, an illustrative construction of a clutch pack composed in combination of a one-way clutch and a friction clutch is shown in section in FIG. 5, which shows: a one-way clutch 10, a friction clutch 20 for establishing engagement or disengagement between an inner ring 1 of the one-way clutch and a counterpart member 15, sprags 2, an outer ring 3, splines 4 of the outer ring 3, splines 5 of the counterpart member 15. a snap ring 6, a packing plate 7, friction plates 8, separator plates 9, a clutch-operating piston 11, O-rings 12, a return spring 13 for the piston 11, and a spring seat 14.
When the friction clutch 20 is engaged by extending the piston 11, rotation of the inner ring 1 only in a specific direction is transmitted to the counterpart member 15 via the one-way clutch 10.
FIG. 6 is a front view of a one-way clutch 10 with the inner ring 1 and the outer ring 3 assembled together, and FIG. 7 is a cross-sectional view taken in the direction of arrows VII--VII of FIG. 6. These drawings illustrate the inner ring 1, the sprags 2, the outer ring 3, the splines 4, cages 31, end bearings 32, a ribbon spring 33.
In a one-way clutch, an inner circumferential wall of an outer ring, with which sprags are brought into contact upon transmission of a torque, in other words, a raceway surface for the torque transmitting members has been subjected to hardening in order to increase its strength. FIG. 8 depicts the state of conventional hardening. As is readily appreciated from FIG. 8, it has been the conventional practice to apply hardening to a uniform depth in an inner circumferential wall of an outer ring, in other words, in a raceway surface for torque transmitting members. Numeral 41 indicates a hardened portion. In FIG. 8, those parts of the one-way clutch which are the same as or equivalent to corresponding parts in FIGS. 6 and 7 are shown by the same reference numerals. Accordingly, FIG. 8 shows the one-way clutch 10, the inner ring 1, the sprags 2, the outer ring 3, the splines 4, the cages 31, the end bearings 32, the ribbon spring 33, and retainer plates 34.
For this heat treatment, i.e., hardening, induction hardening has been applied, for example.
The application of heat treatment to an inner circumferential wall of an outer ring as described above is an effective method from the standpoint that the inner circumferential wall, namely, a raceway surface for torque transmitting members such as sprags be protected from wearing. The outer ring is however configured such that a main body, which comprises the raceway surface for the torque transmitting members and a base portion for a outer ring mounting part 35, and the outer ring mounting part 35 are different in thickness in the direction of an axis of the outer ring 3 and, moreover, the outer ring mounting part 35 is asymmetrical with respect to a perpendicular (a line X-X' in FIG. 8) to the axis as viewed in a cross-section taken in the direction of the axis of the outer ring, said perpendicular extending through a center of the axis of the outer ring. When a stress is applied during use, the outer ring mounting part 35 undergoes greater deformation on a first side (a side A in FIG. 8) of the perpendicular X-X' than on a second side (a side B in FIG. 8) of the same perpendicular X-X' because the outer ring mounting part 35 is smaller in thickness on the first side (i.e., the side A) than on the second side (i.e., the side B). Through repeated use, stress concentrates on the first side (i.e., the side A) as is shown in FIG. 9. The outer ring 3 is hence deformed and is eventually broken. This leads to the inconvenience that the service life of the outer ring is shortened.